Arc chute



Sept. 9, 1947. w. M. scorT, JR

ARC CHUTE Filed Jan. l2, 1945 99 INVENTOR.

M M .Scor-7; Je BY 0- O O O. .n O QQ\ Patented Sept. 9, 1947 UNITEDSTATES PATENT OFFICE ARC CHUTE William M. Scott, Jr., Bryn Mawr, Pa.,assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., acorporation of Pennsylvania Application January 12, 1945, Serial No.572,554

3 Claims. 1

My present invention relates to circuit interrupters and moreparticularly to a novel arc quencher therefor comprising a plurality ofspaced plates of insulating material arranged above and parallel to thearc, the said plates being intersected by a number of transversemetallic rods.

This application is a continuation in part of application Serial No.550179, filed lAugust 19, 1944, and relates specifically to a specialarrangement of the transverse metallic rods so that they are closertogether at the upper portion of the arc chute and so that they are moreclosely spaced along the back and front regions of the arc chute. Thus,the distance between the transverse metallic rods is decreased as thedistance from the point of initiation of the arc increases.

In the construction and operation of circuit interrupters, it isfrequently necessary to provide means for extinguishing quickly the arcwhich is drawn between the contacts as they separate. Such circuitinterrupters, which may be tripped open on the incidence of highcurrents, comprise a pair of main contacts (to carry the full currentduring normal operation), which are arranged to make after and breakbefore a pair of parallel arcing contacts so that any arcing which mayoccur will not pit or otherwise destroy the contact surfaces of the maincontacts.

The arc which is drawn between the arcing contacts when they separateunder over-current conditions is blown upwardly by blow-out means, suchas a magnetic blow-out or air blast (both well known in the art) into anare chute which is arranged to quench the arc by lengthening the same orcooling it, by a combination of these methods or in any other ways.

Arc chutes having spaced insulating plates to lengthen the arc orsqueeze the arc into narrow slots are well known. Arc chutes whichconsist of spaced metallic plates or their equivalent which break thearc up into a number of small arcs in series and move the arc rapidlyacross cooling surfaces, are also well known.

My prior application Serial No, 550,179 contemplated as its essentialfunction the provision of an arc chute which utilized both the principleof spaced insulating plates to lengthen and squeeze the arc, togetherwith a series of metallic surfaces formed by a series of transversepins, each of which extends through all of the insulating plates andwhich are so arranged that the arc is brought into contact therewith andbroken up into a series of small arcs and cooled.

The specic improvement and object of my present invention is thearrangement of these transverse pins so that they will be progressivelymore closely spaced as the distance from the contacts between which thearc is initially drawn is increased.

A corollary object of my invention is the provision of means inconnection with such a spaced plate transverse pin arc chute for movingthe arc readily into the chute and then rapidly cooling andextinguishing the same.

Another object of my invention is the provision of novel arc chuteextinguishing plates.

These and many other objects of my invention will become apparent in thefollowing description and drawings in which:

Figure 1 is a cross-sectional View taken on line I-l of Figure 2 lookingin the direction of the arrows.

Figure 2 is a front View of the elements of the arc quencher takenfromline 2-2 of Figure 1.

Referring now to Figures l and 2, there is here shown an arc quencher 20having generally the construction and operation of the arc quenchershown in my Patent No. 2,348,228, dated May 9, 1944, assigned to theassignee of the present invention. The arc chute 20 comprises a pair ofside supporting plates 2l, 2| of insulating material, between which aremounted a number of spaced arc extinguishing plates 23, 24, 25, 2B, 2l,also of insulating material. The plates are integrated as a single unitby the transverse rivets 3D and 3| which are provided with insulatingbushings 35.

Rivets 30 and 3l are also provided with individual insulating washers orspacers 31 to maintain the spacings between the insulating plates.

The side plates 2l, 2l also carry between them on the transverse bolt 44the back arcing horn 45; and on the transverse bolts 40 and 4I the frontarcing horn 42 and its extension 43.

Current enters the circuit breaker, which is here shown in fragmentaryView, through the stud and passes to the main stationary contact 6l tothe main movable contact 62 mounted on the movable contact arm 63.Appropriate means, such as pigtail connections or other members, may beutilized to carry the current from the main movable contact 62 into theopposite back connection stud, not shown.

The contact members are so arranged that the main movable contact 62will separate from the main stationary contact 6l before the movablearcing contact 65 separates from the stationary arcing contact 66. Whenthe main contacts 6l and 62 have separated, current flows from the stud60 through the angle member 68 to the stamerma' 3 tionary arcing contact06, which is situated at the lower end 69 of the back arcing horn 45,then to the movable arcing contact 65, which is carried by the movablecontact arm B3, and then through a pigtail or other suitable connectionto the opposite terminal, not shown.

As the arcing contacts 66 and 65 separate, an are is drawn therebetweenand is transferred to the arcing horns 45 and 42 by suitable blow-outmeans, preferably magnetic, which are wellknown in the art. are so wellknown, they are not here shown but may comprise the blow-out means shownin my application Serial No. 550,179' or in my Patent When the arc isblown up on the arcing horns 45 and 42, the current path is from'thestud 60 through the angle member 68, the lower end 69 of the arc horn 45to the are horn 45, then across the arc to the arc horn 42 through theextension 43` of the arc horn 42 to the connecting member l0, to which apigtail '1| is connected, in order to permit current to flow to theopposite terminal of the circuit breaker.

The are extinguishing plates 23 through 2l are here shown assubstantially V-shaped plates, the lateral edges t of whichsubstantially parallel the principal portions ofthe arcing horns 45 and42, and the lower ends 8| of which arel convexly rounded at the regionfirst presented to the arc. The plates 23' to 21 are not directly incontact with the arcing horns but a small space' 82 is left between theedges oi the plates andthe arcing horns on each side.

The arc quencher 20 is particularly characterized by a large number oftransverse copper pins |00, |00 which pass through perforations in theplates 23 through 2l, as shown in FigureslV and 2, and which aresupported by' the plates 23 through 2l. The pins preferably do notcontact the opposite supporting insulating members Zl-ZI. This willfacilitate assembly and adjustment of the unit, permits the pins to bebrought down close to the contacts which form the arc, removes thepossibilityl of breakdown or creepage along the supporting plates 2|, 2The remainder of the structure shown corresponds to the circuit breakershown in my Patent No. 2,348,228.

The particular advantages of the transverse copper pins I 00 have beenspecifically described in my application Serial No. 550,179 abovereferred to, and my theory o1" the specific operation of these pins toobtain extremely fast arc extinguishment has also been set forththerein.

The specific contribution of the present invention, apart from the novelextinguishing plate shown is the staggering of the pins |00. Thus, pins|00d are relatively widely spaced from each other. Pin leila is arrangedat the very center of the lowest portion of the arc chute in order tointercept the arc and break it serially into two substantially equalarcs. As the arc moves up to the position indicated by the dotted lineA, pins lilllaZ and |0903 will also intercept the arc, and the arc atthis instant should be broken serially into substantially four arcs inseries.

As the arc is moved up once more, one of the four series arcs of arc Awill move into engagement with one ol the pins |001?. The arc will thenhave the approximate form shown by the dashed line B of Figure 1. As thearc moves upwardly, arc B may then pass from the arc horn 42 to the pin|00a3, to the pin |00b1, to the pin |00a2, to the arc horn 45,`

Since such blow-out meansv As the are is blown up still more, it mayintercept still other pins and thus in a third position assume thecondition shown by line C. In this case, the small arc between pins|001)1 and |00?)2 has been intercepted by pin |00c2 and the small arcbetween pin |00a3 and arc horn 42 has been intercepted by pin |00172 sothat the arc C now passes from the arc horn 42 to pin |00b2, then frompin |0002, then to pin |00b1, and so on, as shown in the figure.

As the arc moves upwardly again to the position shown, for instance, atD, more pins are intercepted and the short series arc are much smaller.The short arcs are at all times subject tothe blow-out which causes thearc as a whole to rise. But, it will be seen that the shorter arc maytend to resist further upward movement, since that would require unduelengthening thereof. Accordingly, the upper pins |00d are much moreclosely spaced than the lower pins |00a and the spacing of the pins isprogressively lessened, as noted, `so that the top-most pins |00e areseparated by much less than half the distance between the pins |00a. Bythis means, therefore, as the number of the arcs in series is increasedand as the length of these arcs becomes relatively smaller, the spacesbetween the pins is progressively decreased so that a greater number ofpins is introduced in series with the arcs, the number of arcs isincreased, and the cooling effect described in application` Serial No.550,179 is greatly' enhanced.

Not only arethe upperV pins Illllel progressively more closely spacedthan the' lower pins, but also I have found that a lateral progressivespacing is closer spacing of the pins adjacent the arcing horns permitsthis upwardly arched position of the arc `to be assumed; that is, theportions-of theA are at position E, which are adjacent to the arcinghorns 42 and 45, are downwardly directed,

and the close positioning of the' pins adjacent to' the arcing horns 42and 45 permits the spacing of the pins to be somewhat similar withrespect to arc E at the portions of the arc adjacent-the arcinghorns 42and 45'.

By' this structure, therefore, the are is first squeezed into one ormore slots which extendparallel to the are path and into which the arcas a whole is squeezedbetween insulating plates. When squeezed into theslots" between these insulating plates, the arc encounters a largenumber of spacedltransverse pins. These pins break the are up into aseries of small arcs between them and, by reason of the rapid movementof the ar'c with respect to the surfaces of these pins and upwardly from`pin to pin, tend to` cool` the roots of the small series arcs. Thistends quickly to extinguish the arc:

Furthermore, since each pin extends through-

